Square shoulder metering rod

ABSTRACT

A metering rod assembly for a pressure sensitive droop flow pump is provided. The assembly includes a metering rod having a first section with a first diameter and a second section with a section diameter, the second diameter larger than the first diameter. A shoulder is formed at a junction of the first section and second section, the shoulder extending radially perpendicular to the first section.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional Patent Application Ser. No. 61/621,798, filed Apr. 9, 2012, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The following description relates to a metering rod, and in particular, a metering rod in a pressure sensitive droop flow pump.

A pressure sensitive droop flow pump may be used in hydraulic power steering pump applications and include a pressure sensitive droop flow control device, such as a metering rod. The pressure sensitive droop flow control device operates according to power steering system pressure. At low engine speeds, and when a pressure increase is detected, the metering rod moves to a position allowing power steering flow to increase, thereby allowing reduced effort to perform steering operations. At higher speeds, the metering rod moves to a position where flow drops, or “droops,” to provide fuel economy savings.

With reference to FIG. 1, a metering rod 10 may include a small diameter section 11 and a larger diameter section 12, with a transition section 13 between the small diameter section 11 and the large diameter section 12. The small diameter section 11 is positioned in an opening 14 in a fluid conduit 15 to allow for increased flow, due to a difference in size between the small diameter section 11 and the opening 14. The metering rod 10 moves to another position so that the large diameter section 12 is positioned in the opening 14 to allow for drooped flow. The drooped flow is a result of the reduced difference in size between the opening 14 and the large diameter section 12.

Typically, the transition section 13 extends at a smooth transition angle a between the large diameter section and small diameter. That is, the transition section 13 typically extends along a length of the metering rod 10 between the small diameter section 11 and larger diameter section 12, and increases in diameter along the length from the small diameter section 11 to the large diameter section 12, thereby forming a generally conical transition section 13. The transition angle a, formed between the small diameter section 11 and the transition section 13, is typically greater than 135°, but may vary slightly to provide a gradual transition between the small diameter section 11 and large diameter section 12 that has a length dimension “L” along the length of the metering rod 10.

However, the conical transition section 13 has limitations with regard to fuel economy. For example, when the metering rod 10 moves from the position where the small diameter section 11 is positioned in the opening 14, i.e., the increased flow condition, corresponding to a low angular velocity (RPM) of the engine and pump, to the position where the large diameter section 12, i.e., the drooped flow condition, corresponding to a higher RPM of the engine and pump, flow is not drooped until the large diameter section 12 is positioned in the opening 14. That is, increased flow may still occur during the time the conical transition section 13 is passing through the opening 14. Thus, increased flow may occur for a period of time while the angular velocity of the pump and engine increase when the drooped flow condition is desired. As a result, excess fuel may be used during the time when the conical transition section 14 passes through the opening 14, resulting in inefficient use of fuel.

Accordingly, it is desirable to provide a metering rod in a pressure sensitive droop flow pump that may transition between a higher flow to a drooped flow in a reduced range of angular velocity (RPM) of the pump and engine to improve fuel economy.

SUMMARY OF THE INVENTION

According to an exemplary embodiment of the present invention, there is provided a pressure sensitive droop flow pump having a fluid conduit having a partition with an aperture formed therein and a metering rod. The metering rod includes a first section having a first diameter and a second section having a section diameter, the second diameter larger than the first diameter. A shoulder is formed at a junction of the first section and second section, the shoulder extending radially perpendicular to the first section.

According to another exemplary embodiment of the present invention, there is provided a metering rod assembly for a pressure sensitive droop flow pump. The assembly includes a metering rod having a first section with a first diameter and a second section with a section diameter, the second diameter larger than the first diameter, and a shoulder formed at a junction of the first section and second section, the shoulder extending radially perpendicular to the first section.

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a metering rod having a conical transition section between a large diameter section and a small diameter section installed in a pump;

FIG. 2 illustrates a metering rod according to an exemplary embodiment of the present invention;

FIG. 3 illustrates a metering rod according to another exemplary embodiment of the present invention; and

FIG. 4 illustrates the metering rod of FIG. 2 installed in a pump according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

Referring now to the Figures, where the invention will be described with reference to specific embodiments, without limiting same, FIG. 2 shows metering rod assembly 20 for pressure sensitive droop flow pump according to an exemplary embodiment of the present invention.

Referring to FIG. 2, in an exemplary embodiment, the metering rod assembly 20 includes a metering rod 22 and a housing 24. The housing 24 includes a cavity to receive a portion of the metering rod 22 therein. The metering rod 22 extends along a longitudinal axis ‘A’ and is reciprocally movable along the longitudinal axis ‘A’ partially into and out of the housing 24.

The metering rod 22 includes a first section 26 and second section 28. In an exemplary embodiment, the first section 26 has a first diameter D1 and the second section 28 includes a second diameter D2. The second diameter D2 is greater than the first diameter D1. In addition, the first section 26 is positioned proximate to the housing 24, while the second section 28 extends from the first section 26 at a distal portion of the metering rod 22.

Still referring to FIG. 2, in an exemplary embodiment, a shoulder 30 is formed at the junction of the first section 26 and second section 28. In an exemplary embodiment, the shoulder 30 is formed as a square shoulder. That is, the shoulder 30 is formed by the second section 28 extending radially outward from the first section 26 at a 90° degree angle, shown as θ in FIG. 2. Said differently, the shoulder 30 extends outwardly in a direction perpendicular to the first axis ‘A’ to form an axially facing wall at the junction between the first section 26 and second section 28. Thus, shoulder 30 presents an axially facing wall at the junction of the small diameter section 26 and the large diameter section 28.

In an exemplary embodiment, the first section 26 and second section 28 are formed as generally cylindrical sections. It is understood however, that variations in the shape of these sections are envisioned. For example, the first and second sections 26, 28 may respectively include beveled or chamfered sections 32, 34 at end portions, away from the shoulder 30. The metering rod 22 may also include a stop flange 36, positioned between the first section 26 and the housing 24. The stop flange 36 may act as a stop to define a travel distance of the metering rod 22 along the axis ‘A’ by abutting adjacent elements.

In the exemplary embodiments above, the shoulder 30 extends perpendicularly from the first section 26 and/or axis ‘A’. However, it is understood that slight variations in the angle θ are also envisioned, for example, for manufacturing purposes. Further, and with reference to FIG. 3, the shoulder 30 may be formed as a stepped shoulder 130, including at least one square step between the first section 26 and second section 28.

FIG. 4 shows the metering rod assembly 20 of FIG. 2 installed in a pump 38 according to an exemplary embodiment of the present invention. In an exemplary embodiment, the pump 38 is a pressure sensitive droop flow pump. Operation of the pump 38 is tied to operation of an engine of the vehicle (not shown) so that the pump 38 operates a fixed ratio relative to the engine. That is, the pump 38 operates at an angular velocity (RPM) that is a fixed ratio with an angular velocity of the engine (not shown).

The pump 38 includes a fluid conduit 40 having a first chamber 42, a second chamber 44 and a partition 46 with an aperture 48. Fluid communicates between the first and second chambers 42, 44 through the aperture 48. That is, a flow path for a fluid in the pump 38 is defined in the fluid conduit 40 in the first chamber 42, aperture 48 and second chamber 44. In an exemplary embodiment, the aperture 48 is generally circular in shape and has a third diameter D3. The third diameter D3 is greater than the second diameter D2.

The metering rod 22 is configured for reciprocal movement along the axis ‘A’ between a first position and a second position within the fluid conduit 40 and through the aperture 48 to control flow of the fluid through the fluid conduit 40. For example, in a high flow rate condition, in the first position, when an engine and the pump 38 are operating at a low angular velocity (RPM), the first section 26 of the metering rod 22 is positioned in the aperture 48. In the high flow/low RPM condition, reduced effort is needed to perform steering operations.

In a low flow condition, the metering rod 22 moves linearly along the axis ‘A’ to the second position so that the second section 28 is positioned within the aperture 48. Due the larger second diameter D2 within the aperture 48, flow of the fluid within the pump 38 is restricted, such that the flow rate is reduced or “drooped”.

Compared to a metering rod in a typical pressure sensitive droop flow pump, for example, as shown in FIG. 1, the metering rod 22 in the pump 38 according to an exemplary embodiment of the present invention may droop flow at a lower angular velocity (RPM) due to the square shoulder 30. This is due in part to the reduced distance between the first section 26 and second section 28 as compared to the distance between the small diameter section 11 and larger diameter section 12 in the typical metering rod. That is, according to an exemplary embodiment of the present invention, the conical transition section 13, having a length ‘L’ in the typical metering rod 10, may be eliminated by using the square shoulder 30 in the metering rod 22 of the present invention. Accordingly, the distance traveled, and thus time, may be reduced to move from the high flow condition where the first section 26 is positioned in the aperture 48 to the low or drooped flow condition where the second section is positioned in the aperture 48. Fuel efficiency may be improved by drooping the flow in a smaller angular velocity range. In addition, by drooping the flow over a lower angular velocity range, the fluid flow may remain consistent during most driving conditions.

In one example of an implementation of the exemplary embodiment described above, high flow scenario may generally refer to a first fluid flow rate through pump 38, for example, approximately 14 lpm. The drooped flow scenario may generally refer to a scenario where flow is reduced or drooped to a second flow rate, for example, less than 10 lpm. When the metering rod 22 with the shoulder 30 moves from the first position to the second position where the second section 28 is positioned in the aperture 48, fluid flow through the pump 38 may be reduced to the second flow rate over an increase of angular velocity, for example, of 1200 RPM in the pump 38, thereby transitioning from the high flow scenario to the drooped flow scenario. That is, the flow rate may be sufficiently drooped over an increase from a first angular velocity to a second angular velocity of, for example, 1200 RPM in an exemplary embodiment of the present invention.

It is understood that the present invention is not limited to the example above. Similar results and advantages may be realized using the metering rod 22 with the square shoulder 30 in environments having different ranges of angular velocities and flow rates. In addition, the metering rod 22 may be tuned to specific applications by altering relative dimensions and positions of the different components while maintaining the square shoulder 30. That is, the metering rod 22 of the present invention may be used under different operating parameters than those described in the example above to droop flow to a suitable level within a suitable angular velocity range across different applications, while still realizing benefits of doing so described herein.

In contrast, with the typical metering rod 10 having the conical transition section 13, an increase in angular velocity of the pump of about 5000 RPM is required to reduce fluid flow through the pump from around 14 lpm to less than 10 lpm. As described above, according to an exemplary embodiment of the present invention flow may be sufficiently drooped over a range of about 1200 RPM. Due the reduced angular velocity range using the square shoulder metering rod 22 of the present invention, fuel efficiency may be improved.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description. 

Having thus described the invention, it is claimed:
 1. A pressure sensitive droop flow pump comprising: a fluid conduit having a partition with an aperture formed therein; and a metering rod comprising a first section having a first diameter and a second section having a section diameter, the second diameter larger than the first diameter, and a shoulder formed at a junction of the first section and second section, the shoulder extending radially perpendicular to the first section.
 2. The pressure sensitive droop flow pump of claim 1, wherein the metering rod extends along an axis, and is reciprocally movable along the axis within the fluid conduit.
 3. The pressure sensitive droop flow pump of claim 2, wherein the metering rod is movable along the first axis between a first position where the first section is positioned in the aperture and a second position where the second section is positioned in the aperture, to control a flow of fluid in the fluid conduit.
 4. The pressure sensitive droop flow pump of claim 3, wherein the fluid flows through the pump at a first flow rate with the metering rod in the first position, and the fluid flows through the pump at a second flow rate with the metering rod in the second position, wherein the second flow rate is less than the first flow rate.
 5. The pressure sensitive droop flow pump of claim 4, wherein the pressure sensitive droop flow pump operates at a first angular velocity with the metering rod in the first position and a second angular velocity with the second position, the second angular velocity is greater than the first angular velocity.
 6. The pressure sensitive droop flow pump of claim 1, wherein the shoulder includes at least one step.
 7. The pressure sensitive droop flow pump of claim 1, wherein the shoulder is formed by a difference between the first diameter and the second diameter at the junction of the first section and the second section.
 8. A metering rod assembly for a pressure sensitive droop flow pump, the assembly comprising: a metering rod having a first section with a first diameter and a second section with a section diameter, the second diameter larger than the first diameter, and a shoulder formed at a junction of the first section and second section, the shoulder extending radially perpendicular to the first section.
 9. The metering rod assembly of claim 8, further comprising a housing configured to receive a portion of the metering rod, the metering rod extending along an axis and configured for reciprocal movement along the axis into and out of the housing.
 10. The metering rod assembly of claim 8, wherein the shoulder includes at least one step.
 11. The metering rod assembly of claim 8, wherein the shoulder is formed by a difference between the first diameter and the second diameter at the junction of the first section and the second section. 